Traditionally, carbon black has been used in tires to make them conductive and therefore antistatic. Carbon black however may cause hysteresis losses that compromise tire properties such as rolling resistance and handling. To improve fuel economy of automobiles attempts have been made to decrease the rolling resistance of a tire. One major solution has been to use tread rubber compositions having silica as a reinforcing material at the expense of carbon black. Although tread rubber compositions comprising silica may provide increased braking ability on wet roads and decreased rolling resistance, they are generally poorly conducting, which may lead to undesired accumulation of electrical charges on an automobile body. With poorly conducting is meant an electrical resistivity at room temperature of higher than 108 ohm-cm after vulcanization.
Antistatic vehicle tires have been proposed that comprise a poorly conducting tread layer and a conductive tread base layer arranged underneath the tread layer, whereby the ground contacting surface is electrically connected to the conductive tread base layer by providing an electrical connection between the two. EP 0718127 B1 for instance discloses a vehicle tire, wherein the tread base layer comprises chimneys that extend radially outward to the tire ground contacting surface to make the electrical connection.
Although some improvements in antistatic behavior are obtained in the known tire, this generally goes at the expense of other tire properties, such as rolling resistance, handling and durability. The conductive chimneys created between the ground contacting surface of the tread layer and the tire conductive base layer divide the tread layer in a number of mutually separated sections. This construction may weaken the tires and their durability is compromised, for instance because the conductive chimneys of the base layer in between the tread sections tend to separate therefrom in use. It has proven difficult to combine these antagonistic properties into one tire and most tire designs have focused on one of the properties mentioned.